One of the all-time classic pieces of GM assistance was the Wandering Damage System, printed in Dragon magazine #96,
an April Fool's issue. It's simply too useful to keep secret any longer, so here it is in all its glory:

How To Use The Wandering Damage System

First there was the wandering monster. They serve well when applied in hordes, but why not cut out the middleman and just deal
out damage to the characters directly? It makes for a smoother, faster-paced game, and if you want to kill off characters quickly, it
can only be beaten by divine intervention by Cthulhoid godlings.

Instructions: Whenever a player annoys you in any way, by wearing tasteless clothes or eating the last corn chip, ask him to roll a
d20. He may become worried that he's rolling a saving throw.
Ha, ha!!! Little does he know that he just rolled on the Wandering Damage System matrix!!! Repeat the roll as often as desired.

The Wandering Damage System Matrix

Roll

Result

1

Your character has fallen down a flight of stairs; roll his dexterity or less on percentile dice, or else consult Limb Loss Subtable.

2

The monster your character just killed gets up and attacks him, doing 8-80 points of damage.

3

Your character smells smoke; his right arm is on fire. Take 14 points of damage and save vs. gangrene.

4

Your character cuts himself while shaving; consult Limb Loss Subtable.

Your character develops an incredibly severe case of arthritis and can grasp nothing with his hands; he drops anything he's holding - and if that happened to be a sword or an axe, consult the Limb Loss Subtable.

Take 10 hit points damage and roll again on Wandering Damage System Matrix.

31-35

Take 15 hit points damage and then take 30 more.

36-40

Roll every die you own for damage.

41-45

Take 17 hit points damage.

46-50

Take 42 hit points damage.

51-55

Multiply your character's age by 5. Take three times that much damage.

56-60

Take 24 hit points damage and then take 31 more.

61-65

Take 1,000 hit points damage and roll again.

66-70

Roll every die within 30 feet for damage.

71-73

Add up the total hit points of everyone in the party. Take that much damage.

74-75

Take 3 hit points damage and consider yourself very lucky - for the time being.

76-00

What? You didn't get hurt? That's impossible - this system is foolproof. Roll again.

(Wandering Damage System is copyright TSR April 1985 and reproduced here as a small extract from an entire magazine for purposes of review
and parody.)

Transcript

{Obi-Wan's fighter lands on Utapau}GM: Obi-Wan, an alien greets you at the Utapau landing platform.Yoda: Ooh, let me describe him!GM: Okay then.Yoda: He's tall and grey, with sharp spiky teeth, and cuts all up and down his face.Obi-Wan: Ew. What happened to your face?Tion Medon: Er... Shaving accident.Obi-Wan: Ah yes, some Jedi are known to shave with their laser swords.Tion Medon: Yet you have a beard.Obi-Wan: Yes. And a head still attached to my neck.